Sue Blackmore, interview with Dave Chalmers
from her book "Conversations on Consciousness", Oxford University Press, 2007

Sue

What's the problem? What makes consciousness such an interesting and difficult thing to study?

Dave

The heart of the science of consciousness is trying to understand the first person perspective. When we look at the world from the perspective of science, we take a third person perspective. We see a subject as a body with a brain, and with certain behaviour. We can be terribly objective, but something very important about being a human being is left out. As human beings we all know that it [emphasis] feels like something, from the inside. We have sensations, thoughts, and feelings.

You might say that there is this amazing movie which seems to be playing inside our mind - more wonderful than any movie you can actually go to in the theatres. It doesn't just have images and sounds. It has emotions and thoughts and the sensation of a body and all kinds of altered states which come around at different times. We all know this, and it's central to being a human being, but for some reason, in the last 50 or 100 years science has tended to ignore this.

Sue

You can understand why can't you? It's very difficult to deal scientifically with the subjective experience of [emphasis] feeling like me now when it doesn't fit in at all with the study of neurons and brains.

Dave

Sure, science is meant to be objective, and consciousness is subjective. So you might say that therefore science can't deal with consciousness. I think that's a fallacy.

A hundred years ago, psychology started as a science of consciousness. In fact the German psychologists conceived of what they were trying to explain in terms of a subject's internal conscious states. They developed detailed introspective methods, and collected data that way, but they descended into squabbles between different camps using idfferent methods which yielded different conclusions. People got fed up with this becaues it seemed hard to settle the debates. Then, early in the twentieth century, the behaviourists took over. They said that from now on psychology is the study of human behaviour. Perhaps this made for a more rigorous and appreachable kind of science. But many people feel that it is somehow like Hamlet without the Prince of Denmark. We are missing the central thing which we are trying to study.

So now I guess the question is how to bring consciousness back into the scientific world. My own attitude is that consciousness is data. As scientists we are used to talking about data and the results of certain measurements, and we try to build a science that deals with them. Usually these are objective data, but we have subjective data too. The data of consciousness - the way things seem to me right now- are data too. I am having a certain sensation of red with a certain shape right now, I am hearing a certain quality in the tone of my voice and so on. This is as undeniable as the objective data in the world of science. And science ought to be dealing with that.

Sue

But isn't there a difference - an enormous gulf - between the subjective and the objective? Aren't they totally different kinds of things?

Dave

Yes, on the face of it they are enormously different things. So the question is, of course, one of the crucial questions in this field, 'How are we going to be able to explain subjective experiences in terms of the objective processes which are familiar from science? How do 100 billion neurons interacting in the brain somehow come together to produce this experience of a conscious mind with all its wonderful images and sounds?

I think right now nobody knows the answer to that question. One could argue about whether such a reduction of subjective experience to a physical process is going to be possible at all. One thing that does seem likely is that we will find correlations. So when I hvae a certain colour sensation or a certain kind of emotion, there are going to be processes in the brain that go along with that kind of subjective experience. But that would be at the level of correlation. What we would eventually like is an explanation. That is, we would be able to look at the physical processes in the brain, and say, 'Aha! Now I see why this gives rise to a subjective experience of this kind.' Right now nobody has a clue about that.

Sue

Do you have any sense of what such an explanation would look like? I mean an explanation of how one arose from the other that would satisfy you, and that you would say was more than just a correlation?

Dave

We do have analogies in other domains, of course. So when it comes to explaining the gene or explaining life, we have an explanation of what DNA molecules do - how they affect other processes in the body, how they lead to certain kinds of development, how they pass on information. Once we see that story we say, 'Aha! OK! That's all there is to being a gene. That explains what we needed to explain.' The question is whether we can do that for consciousness.

My own view is that we can't. Take the analogy with genes - what ultimately gets explained are the various different behaviours and functions which are associated with them. So you might say for consciousness, 'We'll explain the various behaviours and functions associated with consciousness. We'll explain how it is that my eye distinguishes and separates different sensory stimuli, how my brain integrates that information, how that leads to certain kinds of verbal reports and responses on my part.' But when it comes to consciousness those are the easy problems. Those aren't the central thing we are trying to explain. The hard problem is the question of explaining how it is that all this is accompanied by subjective experience. That seems to go beyond any mechanistic question about how the various behaviours and functions are produced.

Sue

You have made an analogy here with trying to understand life. Some people say that consciousness is going to be just the same - that when we really understand all the mechanisms in the brain we'll understand consciousness. Why don't you think it's like that? Don't you think that if you went back, say 200 years, when people were talking about the élan vital and the life principle and what have you, they might have said just what you are saying now, 'I can't see how any understanding of chemistry inside a body would help me understand life - it's a different kind of thing.' Why isn't that a fair analogy?

Dave

I think there is actually a disanalogy here, and it comes down to what really needs to be explained. When it comes down to explaining life, you say 'Well, what are the phenomena? What do we need to explain?' Biological beings reproduce, they metabolize energy from their environment, they use this in controlling their behaviour, they adapt and they grow. They compete with each other for resources. They evolve. All these are ultimately questions of behaviours and functions. What needs to be explained in each case are these matters of objective function.

Two hundred years ago the vitalists said, 'I can't see how you could have these behaviours, these functions, something as amazing as growth and reproduction. How could dead matter do that?' So they thought you needed to bring in a vital spirit. It eventually turned out that mechanisms could do all that, and so vitalism disappeared. But what's interesting is that this shows what even the vitalists conceded, that when it comes to explaining life, all we needed to explain were objective third person behaviours.

Now with consciousness, things are completely different. We can all agree on what needs to be explained. There's my behaviour and my responses and my reports, sure. And let's all concede, at least for the sake of argument, that science might be able to explain those. The trouble is that we haven't exhausted what needs to be explained. We've left out the central datum; the datum of subjective experience. And that seems to have no analogy in the life case.

Sue

But wait a minute. Aren't some of these 'data of subjective experience' turning out to be illusory? For example, there's the feeling that consciousness [emphasis] does something. This is a very ordinary human experience, in which it seems to me that I consciously decide to do something and then it happens. And yet there are many scientists who say 'Well, actually that's an illusion. These decisions are made, the body acts, but consciousness dosn't have any role.'

Couldn't it be that all these feelings about what conscious experience is, or what subjectivity is, will eventually just disappear, and we'll see them all to be some kind of illusion?

Dave

I wouldn't want to say that people are infallible about the contents of their consciousness, because clearly that's false. For example, you might put an ice cube on my back when I was expecting a match. I could think for a moment that I am having a sensation of hot, but then after a moment I realize that no, actually that was a sensation of cold. But it's one thing to say that we can be mistaken about certain subtle things in the fringes, but could I really be mistaken about the fact that right now I am having a visual experience; a visual image with certain shapes and colours and so on? I think that is just impossible.

Maybe I am wrong about certain subtle features of the image. Maybe, for example, I think there is more going on in the background of my visual image than there really is. But to say 'Well, maybe I'm not really conscious at all,' that seems to be going too far. Descartes, of course, said that this was the one thing we know more certainly than anything else. 'Cogito ergo sum: I think, therefore I am.' What he was really talking about was consciousness.

Sue

And do you agree with Descartes?

Dave

I do agree with Descartes on that. There is no doubting that we are conscious. I think we can only doubt that we have consciousness in philosophical moments - when philosophers are arguing about this and they say, 'Maybe it will turn out that consciousness doesn't exist.' But I think that this is simply going contrary to the manifest data of subjective experience.

Sue

You talked earlier about the 'easy problems' and the 'hard problem', and this distinction is probably what you are most famous for. In fact, everybody now seems to start any discussion of consciousness with an account of the 'hard problem'. Can you tell me how you came to categorize it that way?

Dave

I never thought of this as a terribly profound distinction to make. I thought I was just stating the obvious. I gave a paper at the first Tucson conference on consciousness, back in '94, and early in the conference I got up and wanted to say some substantive things about consciousness. So I thought, 'OK, I'll start by stating the obvious - what needs to be explained is behaviour (those are the easy problems), and subjective experience (that's the hard problem).' Now this was meant to be just the prelude before I went on to say something more profound.

Of course, what everybody remembers are those first five minutes at the beginning. I guess it turned out to be useful for the field to have a short tag for the problem. But now it's taken on a life of its own. I don't think I added anything profound and original, because everybody who really thinks about consciousness knows that the hard problem is the problem of subjective experience, and they have known this for hundreds of years.

Sue

You have described the hard problem as the difficulty of explaining how subjective experience arises from an objective world. Is this the same as the mind-body problem? Is it the same as the problem that leads to Cartesian dualism? Or is it a different problem?

Dave

I think it's in the same ball park. The term 'mind-body problem' covers a multitude of sins. One is this question: How is it that the brain can support subjective expereinces?' Another one is: 'How can the brain support thought, or rationality and intelligence?' Maybe that is not quite the same problem, because it's closer to the domain of behaviour. Another question is: 'How can the mind affect the physical world?' That's very closely related. But they are slightly different problems. We can think of the hard problem as the real core of the mind-body problem.

Sue

And now to those profound bits - what's your own way of tackling the hard problem?

Dave

I am not going to sit here and tell you that I'm now going to say something profound, and then say it! But, OK, I think there are reasons, which I have touched on, for saying that subjective experience can't be reduced to a brain process. No explanation solely in terms of brain processes will be such that we can deduce the existence of consciousness from it. I think someone could know all the physical facts about the world and still not know about consciousness. So if the relationship between brain processes and conscious experience isn't one of reduction, what is it? Obviously there is going to be a very close correlation and a connection. What a science of consciousness needs to do is to systematize that bridge.

This raises deep questions of metaphysics. What is there in the world? What are the basic components of the world? In physics this happens all the time. Nobody tries to explain, say space or time in terms of something which is more basic than space or time. It's the same with mass or charge. They end up taking [emphasis] something as fundamental. My own view is thta to be consistent we have to say the same thing about consciousness. If it turns out that the facts about consciousness can't be derived from the fundamental physical properties we already have, like space and time and mass and charge, then the consistent thing to say is, 'OK, then consciousness isn't to be reduced. It's irreducible. It's fundamental. It's a basic feature of the world.'

So what we have to do when it comes to consciousness is admit it as a fundamental feature of the world - as irreducible as space and time. Then we need to look at the laws that govern it, at the connection between the first person data of subjective experience and the third person objective physical properties. Eventually we may come up with a set of fundamental laws governing that connection, which are akin to the simple fundamental laws that we find in physics.

Sue

I understand that you want to try out the idea that consciousness is a fundamental principle of the universe, but you were talking there about correlations. Most people, when they hear about the 'neural correlates of consciousness', mean that they take one thing (such as a subjective report) - and another thing (such as something they can measure in the brain) - and try to see if they are correlated. Now if you were just saying that, it wouldn't help would it? I take you to be saying something more fundamental than that - that consciousness is not just one more thing that can be correlated, but that it underlies the world in some way, or that it forms a framework.

You made an analogy with space and time, and space and time in physics are basic principles, used to structure everything else. So if you were going to make that analogy work you would have to say something similar about consciousness. Is that what you are trying to do, and can you do it?

Dave

I am not saying that consciousness structures everything else in the world. All I am saying her is that it is a fundamental feature of the world. The question is how can we get to a theory? How can we have something that looks like an explanation of consciousness when we just have these subjective phenomena and these physical processes in the brain? If all we have as our fundamentals is, say, space and time and mass, then consciousness isn't even going to get in to the picture. So we put consciousness in to the picture and we study the correlations.

In this picture, everything that's going on in the study of the neural correlates of consciousness will turn out to be important work. You might say it's going to be even more important, because by studying the correlations between the first person and the third person we are gradually moving towards those fundamental principles which bridge the divide.

Sue

If consciousness is somehow that fundamental a principle, wouldn't you expect it to be ubiquitous? Are you coming close to a panpsychic view here, where everything is conscious?

Dave

I think the view that consciousness is irreducible is neutral in the question of whether consciousness is ubiquitous. You could say that it is irreducible but rare. I mean some fundamental properties are rare. There are huge areas of vacuum throughout space in which there is no mass, for example. So maybe there are huge areas in which there is no consciousness.

It is true, though, that it is natural to speculate. After all, it is very hard to draw the line for where consciousness stops. We think people are conscious, almost all of us think chimps, dogs, and cats are conscious. When it comes to fish and mice, some people might deny it. But fish and mice have perceptual fields and it's plausible that they have some kind of conscious experience. Then you just go further and further down.

My own view is that where you have complex information processing you find complex consciousness. As the information processing gets simpler and simpler you find some kind of simpler consciousness.

Sue

This would lead to a very odd thought though. You say that associated with all kinds of information processing is some kind of consciousness. In a huma being there may be multiple sorts of information processing going on at once - I mean different bits of our brain are doing all these different clever things - and only some of them are what we would call 'my consciousness'. It seems to me you must be saying that there are multiple consciousnesses which I don't know about going on in this brain here.

Dave

Well - this raises some interesting questions about the self and the subject. This is only speculation, but on a panpsychic view Iwould imagine that the kind of consciousness that you would find throughout most of the world is incredibly simple and undifferentiated and not very interesting. Some of the time that basic field of consciousness might come together into unified, coherent, bounded objects that we think of as selves. Now what the conditions are for that, I think nobody knows. Maybe it's got to do with certain kinds of very sistematic, coherent information processing. So that means that in the vicinity of my brain there's this one remarkably coherent system of information processing which corresponds to 'me'. Now, as you say, there are other things going on in my body, and one would have to say that there are experiences associated with those. But those don't give rise to selves or to subjects, and they have nothing to do with me.

Sue

So would they be more like the sort of consciousness in an animal that had no concept of self?

Dave

Or maybe even simpler. Let's look at an incredibly simple system like a thermostat. Who knows? Is a thermostat conscious? It would only be speculation, but just say it was. It would be at best a tremendously simple and primitive form of consciousness. One state here, another state there, but nothing corresponding t owhat we tould think of as thinking, or intelligence, or a self.

Sue

Youre touching here on one of those other problems that has become central in arguments about consciousness. That is, whether a system carrying out some intelligent behaviour would necessarily be conscious by virtue of doing that behaviour. And this comes close to your zombie theory. Would you like to explain about zombies?

Dave

Sure. I think in the actual world, intelligent behaviour and consciousness very likely go together. So when you find a system which is behaving like me and talking like me - it's probably conscious. But it seems that I could [emphasis] imagine a system which was behaviourally just like me, it walked and talked just like me, it got around its environment, but it didn't have subjective experience at all. Everything was dark inside. This would be what philosophers like to call a zombie - a being entirely lacking consciousness.

Now such a being would be tremendously sophisticated. You couldn't tell the difference from the outside, but there would be nobody home inside. Here I am sitting talking to you. All I have access to is your behaviour. Now you seem like a reasonably intelligent human being, you're saying articulate things that suggest a conscious being inside. But of course, the age old problem is 'How do I know?' It's at least logically consistent with my evidence that you are a zombie.

Now I don't think you are, but the very logical possibility of zombies is interesting because then we can raise the question 'Why are we not zombies?' There could have been a universe of zombies. Think about God creating the world. It seems logically within God's powers (and of course the use of 'God' here is just a metaphor) to create a world which was physically just like this one but with a lot of particles and complex systems behaving in complex ways, but these were just androids. There was no consciousness at all.

And yet there [emphasis] is consciousness. So that's been used by some people, including me, to suggest that the existence of consciousness in our world is a further deeper property of the world tahn its mere physical constitution.

Sue

So are you saying that you believe such philosophers' zombies are possible and the fact that we have consciousness means that we have to add something to the explanation?

dave

I think they're probably not possible in the sense that no such thing could ever exist in this world. I think that even a computer which has really complex intelligent behaviour and functioning would probably be conscious. What is interesting though, is that it doesn't seem contradictory to suppose, at least in the imagination, that someone, somewhere, in some possible world could behave like me without consciousness. But our world isn't like that. So that's an interesting fact about our world!

Sue

You say our world isn't like that. Does this make you a functionalist? Are you saying that, in our world, anything that carries out a certain function must necessarily be conscious?

Dave

In some very broad sense I am a functionalist. I think that behaviour, and function, and consciousness go together. They are very tightly associated. But I am not a functionalist in the strong sense of saying that all there is to consciousness is the functioning. Some people say that all we have to worry about is functioning and the behaviour and the talking. I think that is just manifestly false because of the direct data of subjective experience. We have correlation of the two without any kind of reduction of one to the other.

Sue

I want to get this absolutely clear because people talk about your views on zombies a lot. You are saying that logically you can conceive of a world in which there would be intelligent, behaving creatures who went around saying things like 'I am conscious' and 'I'm experiencing red right now' and so on, but didn't have any subjective experience. But you think that in this real world we are in that's not possible and anything that does these behaviours will necessarily be conscious.

Dave

That's exactly right.

Sue

Good!

Now it seems to me that the zombie question is related in an interesting way to the question of evolution - that is, 'Has consciousness evolved for a reason?' Because if zombies were possible in this world then you would have to explain why we aren't zombies. You would have to say'We are conscious, so there must be some function for consciousness, or some reason why evolution added on consciousness.' Whereas if you take your view, that necessarily any system that does all these things must be conscious, then there is no necessity that evolution has produced consciousness for a reason is there?

Dave

Not necessarily, no. On my view, of course, evolution is going to select physical systems for their physical functioning. Once you have a system which functions like that it will be conscious. So therefore consciousness will evolve. But did that system evolve because it was conscious? Was consciousness doing something for that system? I think right now, nobody has any answer to that question.

People put forward speculation - maybe the function of consciousness is planning or decision making or integrating information or whatever. But then as soon as such a hypothesis is put forward the questions just get raised 'Why couldn't that have been done without consciousness? Why couldn't you just have had these brain processes which produced that conclusion with no subjective experience anywhere?' And of course you can use zombies to illustrate this point. You can imagine, at least hypothetically, that zombies could have existed which did the kind of things that we do but without consciousness. Now of course in our world consciousness is here so that is the difference between us and zombies. It does raise the very deep question of what consciousness is for.

One possibility is that consciousness is a non-physical thing that interacts with the physical world, as Descartes thought. It could then be selected for by virtue of its actions. That's regarded as somewhat implausible though, because it comes into tension with our view of the physical world as revealed by physics. Although in turn some people think there is room for it in quantum mechanics.

Maybe there is another way of approaching the question 'Why is there consciousness?' You might say that consciousness is a thing which gives our lives meaning. It makes our lives comprehensible and interesting and a locus of value. And in a world of zombies there would be no meaning.

Sue

You mentioned quantum mechanical approaches to consciousness. Do you think these are valuable?

Dave

I think there are interesting but extremely speculative. One basic problem is this. In classical neuroscience you may have 40-Hz oscillations in the brain, or various interactions, but why should any of that give you consciousness? People can't see how. So they say, 'Ah - we need something new. An extra ingredient. Let's say it's a collapsing quantum wave function in our microtubules.' But now the question comes up again. But why should collapsing wave functions in microtubules give you consciousness? You're not really any closer.

Sue

Do you think you have free will?

Dave

I don't know, I really don't know. And the reason I don't know is that I don't know what it means to have free will.

I know that most of the time when I want to do something I do it, and most of the time that seems good enough. If I want to go down to the grocery store, I can go to the grocery store, except if somebody is locking me up in prison then I can't. But I can, so I am free.

Now someone is going to come back and say, 'Aha, but what you want to do, the fact that you want to go to the grocery store, that was determined all along, and therefore you are not free.' And there are moments when I actually think, 'Well, that worries me. I can't choose what I want, because that is already determined.' But then I just say, 'Well, how else could it be?' Who would want to be able to choose what they want? That is just part of who I am. So maybe this further kind of free will, where one can choose who one is going to be and what one is going to want in some undetermined way, is just an illusory desire and would at the end of the day be useless, because this is who I am.

Sue

Do you feel that your life has been changed by all these years of thinking about consciousness?

Dave

I think it would be nice if the answer were to be 'yes'. I think it affects little things. For a while I was very tempted to become a vegetarian because I didn't want to eat anything which is conscious. Then I started to develop views about consciousness which suggested that it wasn't just cows and pigs and so on which were conscious. Now, if I had still stuck to my principles, I was going to go very hungry. So I said, 'OK, what this suggests is that it's not consciousness that matters, it's complex consciousness that's morally and ethically significant.' So the consequence is that I don't mind eating fish and perhaps chicken and certain simple organisms. I have some qualms there, but I am not totally uncomfortable eating meat, which is probably convenient because I like the taste quite a lot.

Sue

How did you get in to all this in the first place? Have you worried about consciousness ever since you were a kid? Or was there something particular that started you thinking about it?

Dave

I do know that when I was ten I discovered I was short-sighted. It turned out that I had one very good eye, but the other was very bulrry, and one day I got glasses that gave me binocular vision. Now the world wasn't just sharp, it was also deep. And I wondered, 'How does just getting glasses suddenly make the world feel deep?' I could understand it from the third person point of view, but not from the fist person point of view.

Later on, as an undergraduate studying mathematics and physics, I used to sit around the table talking about consciousness all the time with my friends. I thought it was way too much fun that one could actually make it one's profession. It seemed kind of illicit, somehow.

I still think that from time to time. I would have loved to have been a mathematician or a physicist 500 years ago, at the time of Newton when nobody knew anything. That would have been exciting! So many open frontiers! Mathematics and physics are still very interesting, but there is a sense that we've got the basic framework and are filling in the gaps. I wanted to be on one of those frontiers. I was just obsessed at this point by the problem of consciousness, so I made a leap of faith. I got out of mathematics and physics and started trying to turn my wild ideas abotu consciousness in to something vaguely down to earth within the context of being a philosopher and a cognitive scientist. And in the end it seems to have more or less worked out, but that's not to say that anyone is ever great at doing philosophy. It's just too hard.

Sue

I bet you are glad, now, that you had the courage.

Dave

Yeah. You know I have to say it took me a while to work up the courage. For the first year or two while I was talking about doing this, everybody said I was crazy. My family said I was crazy. They said, 'You're pretty good at mathematics. What's all this nonsense about philosophy? Nobody gets anywhere doing philosophy.' But I think it's turned out that I have a more interesting life this way than I ever would have as a mathematicain.

Sue

What do you think happens to consciousness after death?

Dave

I don't know for sure. But I'm inclined to think that my consciousness ceases to exist. Whether or not consciousness is reducible to the brain, my consciousness seems to depend on my brain. Damage my brain, and you damage my consciousness. After death, my brain will disintegrate, so my consciousness will distinegrate too. If a panpsychist view is true, it could be that corresponding to my disintegrated brain will be some disintegrated fragments of consciousness. But I don't think these fragments would count as my consciousness in any recognizable sense. I'll probably cease to exist. Then again, no one understands consciousness, so I could be completely wrong. That would be nice!